[*] basic in-house cpp linting (#4039)

- add `#pragma once` to remainder files
- "correcter" defines (ANDROID), see https://groups.google.com/g/android-ndk/c/cf9_f1SLXls
- extra miscelly fixups

Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4039
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: crueter <crueter@eden-emu.dev>

src/common/cpu_features.cpp

@@ -303,7 +303,7 @@ namespace {
 }
 [[nodiscard]] s64 GetHostCNTFRQ() noexcept {
     u64 cntfrq_el0 = 0;
-#ifdef ANDROID
+#ifdef __ANDROID__
     std::string_view board{""};
     char buffer[PROP_VALUE_MAX];
     int len{__system_property_get("ro.product.board", buffer)};